Laptops, tablets and smartphones have become more than supplements to desktop computers and desk phones—they've evolved into multipurpose mobile unified communications (UC) devices capable of functioning as a user's primary phone, video conferencing endpoint and messaging platform.

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As much as it would please IT organizations, users won't plug these devices into an Ethernet port. In the case of nearly all tablets and smartphones, they simply can't. But users will expect their mobile unified communications applications to perform on the enterprise wireless local area network (LAN) just as well as they would on the wired network, despite the fact that VoIP and video conferencing are far from Wi-Fi-friendly.

Not one user at YES Prep Public Schools, a charter school district for low-income students in Houston, has a traditional desk phone. Faculty and staff have access to the full suite of Microsoft Lync applications—including softphone and desktop video conferencing clients—on laptops they tote around the district's eight campuses.

The reason we didn't have a solution before is there was no problem to solve. We had Wi-Fi phones, but they weren't really all that widely deployed.... The tablet is really going to be a significant driver here.

Zeus Kerravala Senior Vice President and Distinguished Research Fellow, Yankee Group

"Teachers are so mobile in their classrooms, and ... because of [that], they're not going to use [the wired connection] we prefer them to use," said Troy Neal, senior director of IT and support services at YES Prep. "They live on wireless."

But supporting mobile UC services such as VoIP and video conferencing over Wi-Fi has been problematic, according to Zeus Kerravala, senior vice president and distinguished research fellow at Yankee Group. Because a Wi-Fi is a shared medium, UC pros struggle to guarantee the quality of a wireless VoIP call while another user on the same wireless access point (AP) is streaming a YouTube video, he said.

"You can get it to work, but the problem is keeping it working in a way where all of the users are going to be happy and all of the applications are going to perform well," Kerravala said. "That's the evolution the wireless LAN has to make. It has to move from a hub-type architecture to a switch-type architecture ... where every user [gets] dedicated bandwidth."

As wireless LANs graduate from auxiliary to overlay networks and the number of mobile devices continues to multiply, the challenge of supporting mobile UC over Wi-Fi will become "a pretty scary thing" for UC and networking pros, Kerravala said.

"If you look at a lot of the new tablets, they're meant to deliver voice and video," he said. "Wireless is the primary access for that technology—not the augmentation—so as companies look at the wireless LAN, they need to think about it differently. This is not your father's wireless LAN. This is much more strategic than tactical now."

Although VoIP and video conferencing over Wi-Fi has been a longtime challenge, there was no pressing demand from enterprises to solve it until recently, Kerravala said. Broader enterprise adoption of tablets will push mobile UC and wireless LAN vendors to address these issues, he said.

"I think the reason we didn't have a solution before is there was no problem to solve. We had Wi-Fi phones, but they weren't really all that widely deployed," Kerravala said. "The tablet is really going to be a significant driver here."

Mobile UC over Wi-Fi requires more than tagging

As voice and video evolve from dedicated systems into apps that coexist on a converged device, traditional methods of managing UC traffic on a wireless LAN become inadequate, according to Robert Fenstermacher, director of education marketing at Aruba Networks.

Enterprises typically prioritize VoIP and video conferencing traffic by assigning the dedicated devices carrying that traffic to different service set identifiers (SSIDs) than standard data traffic, Fenstermacher said. From there, the traffic is often segmented into separate virtual LANs (VLANs), where policies and prioritization are applied.

"In the case where we have a device like a tablet, laptop or phone that does all of these [mobile UC services] ... what network do I connect it to? What VLAN do I associate it with? Am I over-provisioning network resources to it or under-provisioning network resources?" he said. "Wi-Fi really has not been up to the task of supporting this model."

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Wireless LAN vendors have tried to solve this problem by enabling 802.1e Wi-Fi Multimedia (WMM) tagging, a standard for identifying applications over the air so that wired network devices can properly apply Quality of Service (QoS) policies once the traffic gets to them.

But the problem with WMM tagging is that it's usually too good to be true, Fenstermacher said. The tag is often lost in transport or is untranslatable to other network devices. Many platforms, including Lync, disable it by default, he said.

Working with Microsoft, Aruba recently updated its controllers to apply what it calls its "fingerprinting" technology to detect, identify and prioritize specific Lync applications based on their traffic patterns. Because Lync traffic is encrypted, Aruba's controllers cannot identify it with traditional methods using deep packet inspection (DPI), Fenstermacher said.

Despite the shortcomings of WMM tagging, Aruba still applies it alongside 802.1Q VLAN tagging so that "ideally you have Quality of Service that's applied" throughout the rest of the LAN and wide area network (WAN), Fenstermacher said.

Aruba and Microsoft appear to be the first vendors tackling this challenge, but don't expect them to be the last, according to Yankee Group's Kerravala. Expect competitors Cisco Systems and Avaya to release similar solutions, but they will likely be tailored only for their UC platform and wireless LAN products, he said.

Neal has saturated each YES Prep campus with 48 APs—one in each classroom—and worked with Aruba to implement the Lync-related updates across the controllers on the district's 1 Gbps backbone. The Aruba deployment replaced a legacy hodgepodge of consumer-grade APs and 3G USB modems.

"Our teachers don't even know if they're on wireless or not, and they don't know the difference if they are. That's important with things like video conferencing," he said. "You don't see the difference between being plugged in and not being plugged in."

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